reply to u/Omega48boar at https://reddit.com/r/typewriters/comments/1knsgn8/pressure/
I was wondering what the upper limit psi would be for blowing out the gunk using an air compressor.
The highest air compressor pressures may be determined by your particular compressor's (or air canister's) maximum output as well as the maximum suggested output for any accessories you're attaching to it. Many basic air gun attachments have a max PSI of around 100 PSI even when the compressor will produce much higher outputs.
Generally I find that for most benchwork on typewriters anywhere from 50-100 PSI is generally more than sufficient.
Depending on the condition of your surroundings, I recommend putting a towel (or similar material) underneath your typewriter with a solid backstop so that if any springs, screws, or other valuable parts are blown loose, they're caught pretty quickly by the towel rather than flying across the room or down onto the floor out of sight.
Higher pressure settings may be useful in some cases. One should always take care to be wearing protective garments and eyewear to prevent being spattered with caustic chemicals. Similarly protecting plastics, paint, and decals on your typewriter with appropriate cover is advised with some solvents.
Operating the compressor, which can cause sparks as well as heat, at a reasonable distance from potential flammable vapors is also a mandatory safety precaution. Using volatile solvents frequently seen in typewriter cleaning procedures should only be done in the open in a well-ventilated area using appropriate masks to prevent inhalation of vapors. Long term exposure to vapors of substances like lacquer thinner can cause lung damage, COPD, and other adverse health effects.
For extended usage pending the sorts of air gun tips which might be used for typewriter cleaning, one is also well advised to use ear protection to prevent long term hearing damage/loss.